Solex Issue

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Vic Skirmants
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Re: Solex Issue

#16 Post by Vic Skirmants »

You can access those holes by removing the large brass threaded plug on the opposite side.

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Bruce Smith
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Re: Solex Issue

#17 Post by Bruce Smith »

My suggestion, if all else fails, is to tear them down again completely, spray carb cleaner in every orifice and follow with compressed air. Don't overlook the throat ports near the throttle plates. Then get a pin gauge set and clear out/gauge every jet and nozzle. Only then are you going to be certain that passages are clean AND that the jets are open to what they should be. You can find tear-down diagrams of early and later Solex carbs here: http://www.hillmanimages.com/912/fuel3.html. Pin gauges like this one cover the necessary range: Shar (and others) Pin Gage Set (0.011" - 0.060"), 50 Piece.
Bruce Smith

Greg Garrett
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Re: Solex Issue

#18 Post by Greg Garrett »

Thank you so much, Bruce, and everyone who has chimed in. I will get a pin gauge set and go through the carb completely. After I’m done I will reinstall and report back the results.
Suddenly lots of rain here in NorCal so I will have to wait a bit to get back at it.

Dick Weiss
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Re: Solex Issue

#19 Post by Dick Weiss »

The by-pass holes are under the slotted brass plug next to the bottom of the carb's 'feet'; Another hole is 1/2 way up the throat
on later carbs.

Greg Garrett
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Re: Solex Issue

#20 Post by Greg Garrett »

Good info. I’m hopeful that’s where the problem lies. When you watch the re-boring process, it seems almost inevitable that some tiny pieces of metal shaving would get into those ports as the bit or cutter goes right across the face of those ports. No doubt the machinist blows them out after cutting but a tiny sliver could get wedged in there. The pin gauge that Bruce suggested should verify if I’m right or not.

Dave Erickson
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Re: Solex Issue

#21 Post by Dave Erickson »

Greg, what size idle jets and main jets are you running, and are the carbs originally solid shaft or split shaft?

Also, pay attention to Craig's posts. Especially the one that said even newly rethrottled carbs may not be balanced from side to side. I do this in two stages. When the butterflies are being installed I use a light bench that shines light up through the carb body, it really helps to get the butterflies set identically. Then I verify flow on the bench: I hook up a vacuum cleaner with a valve to regulate the amount of negative pressure, then use a Uni-syn to compare flow on each side with the throttle closed (idle stop screws set equal), then at various off-idle points. About ⅓ of the time I need to twist the throttle shaft to get both barrels breathing the same (unless it is a split shaft which makes that adjustment simple). I posted a photo of the vacuum cleaner setup before, but I couldn't find it so here are a couple to show how easy it is to fabricate a flow bench to make this test.
IMG_4417.jpg
IMG_4420.jpg

Greg Garrett
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Re: Solex Issue

#22 Post by Greg Garrett »

The idles are 57.5...I will check the mains when I get it apart probably tomorrow. These are originally solid shaft as far as I know.
I got the throttle plates from Partsklassik and I assembled both carbs the same day once the machining was done. They went together nicely, the throttle plates look to be even on both carbs and the left carb is operating nicely as near as I can tell. I’m going to try Bruce’s suggestion first and go completely through the affected carb and try it again since it’s so easy to remove and install these.
I have a uni-syn and a synchrometer so I can try both.
If the problem still exists I will try your suggestion, which I appreciate, because at that point I would be looking for more options.

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Craig Richter
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Re: Solex Issue

#23 Post by Craig Richter »

Dave,
Slick little flow bench you assembled there. Normally one has to get out the old Uni-syn, look, listen, and still end up taking the carb(s) off a few times. Nice time saver.
 

Greg Garrett
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Re: Solex Issue

#24 Post by Greg Garrett »

Update:
I took the carb apart to check and clean everything. Along the way I removed the large brass plugs and could see the holes going through to the bore. I looked in there and worked the throttle plates slowly by hand to see if they were visible at the same point on each side through the holes. And then I saw it. On the right side there were 3 holes in line vertically. On the left side (the side that would correspond with the non firing cylinder) there were only 2 holes visible. The bottom hole was not there. This is the one that is the largest hole in the wall on the throttle plate side. I was able to clear it. There wasn’t metal shaving in there but rather a hard grey “crud” for lack of a better word. I’m reasonably sure I got it all cleaned out but the hole is smaller than the one on the opposite side. I’m guessing they should be the same...does anyone know?
I’m going to reinstall the carb and try it as soon as I get some feedback. Thanks

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Doug McDonnell
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Re: Solex Issue

#25 Post by Doug McDonnell »

Keep cleaning you are only 1/2 way there.
1965 356C 2000 BMW 740i Sport 1967 Honda CL77 There is never enough time to do it right, but always enough time to do it over.

Greg Garrett
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Re: Solex Issue

#26 Post by Greg Garrett »

So they should be the same size. Thanks, back at it.....

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John Brooks
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Re: Solex Issue

#27 Post by John Brooks »

Yes the same size, now a set of nedella jet reamers to size the hole. Careful not to enlarge to reshape it.

I like the vacuum flow bench. I have a wet bench to set the floats, looks like I can combine these two. But separate benches, you don't want to draw gas fumes through a shop vac.
Attachments
Small tank, electric pump, P-tools, jet reamers, pressure gauge on a NPT banjo bolt, spare manifolds.
Small tank, electric pump, P-tools, jet reamers, pressure gauge on a NPT banjo bolt, spare manifolds.
John Brooks

62 Roadster
66 912
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getting pushed around in porsches since 1965

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Ron LaDow
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Re: Solex Issue

#28 Post by Ron LaDow »

John Brooks wrote: But separate benches, you don't want to draw gas fumes through a shop vac.
You won't do it twice.
Ron LaDow
www.precisionmatters.biz

Dave Erickson
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Re: Solex Issue

#29 Post by Dave Erickson »

John Brooks wrote:Yes the same size, now a set of nedella jet reamers to size the hole. Careful not to enlarge to reshape it.

I like the vacuum flow bench. I have a wet bench to set the floats, looks like I can combine these two. But separate benches, you don't want to draw gas fumes through a shop vac.
I use the flow bench to collect fluid when I check float height, then dump it back into the can. I've been using paint thinner instead of gas, it is less dangerous.

Greg Garrett
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Re: Solex Issue

#30 Post by Greg Garrett »

Well, good news and bad news. I went in for more cleaning of the formerly plugged port and I’m sure it’s all cleaned. The problem is that the hole under the brass plug on the opposite side has somehow gotten enlarged. At this point not much I could do....I reinstalled the carbs and am now firing on all cylinders.
(That’s the good news). I got the air mixtures dialed in and balanced the carbs with the synchrometer. All barrels look to be drawing equally. Engine runs good at speed but when taking off from a start it “bucks” until it catches and then goes fine. When I changed the plugs I made the mistake of gapping to what is says on the box-.032. But now I see everyone says it should be .026 to .028. They are Bosch
WR7BC+...I’m going to re-gap them and go from there. Also may have to play around with the throttle pump adjustments. I did preset them with the bent straw method but my measuring device, a plugged off plastic syringe, may not be so accurate.

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